/Engine/Source/Runtime/Landscape/Classes/LandscapeProxy.h
Output a landscape weightmap to a render target Only works in the editor
bool LandscapeExportWeightmapToRenderTarget ( [UTextureRenderTarget2D](API\Runtime\Engine\Engine\UTextureRenderTarget2D) * InRenderTarget, [FName](API\Runtime\Core\UObject\FName) InLayerName )